Admission to a hospital when most of the beds are already full can be deadly for patients, according to a new University of Michigan Health System study showing high occupancy increases the risk of dying in the hospital by 5.6 percent.  

For the study, published in the March issue of Medical Care, researchers evaluated a set of critical factors that can affect hospital deaths, including hospital occupancy levels, nurse staffing levels, weekend admission and seasonal influenza.

Having more nurses on staff makes patients safer, according to the study, decreasing hospital death risk by 6 percent. But weekend admission raised the risk by 7.5 percent, while admission during widespread seasonal flu had the greatest impact by increasing the risk of death by 11.7 percent, according to the study.

Because of the size of the study, which included 166,920 adult patients admitted to 39 Michigan hospitals over 3 years, the findings can be generalized to hospitals nationwide, the authors say. Study patients were admitted after being seen in the emergency department for a heart attack, congestive heart failure, stroke, pneumonia, hip fracture or gastrointestinal bleeding.

The researchers calculated the occupancy of the hospitals every day for the years 2003-2006. On average, patients in the study were admitted while hospital occupancy was 73 percent of full capacity. One-third of patients were admitted on high occupancy days, at average levels of 80 percent or more.

According to the authors of the U-M study, it is also the first to illuminate the concept of "access block," a phenomenon thought to occur when a full hospital prevents emergency department patients from accessing an inpatient hospital bed, thus prolonging wait times and delaying time-critical inpatient care.

While a rush of accident victims to the ER is impossible to predict, hospital administrators can, to a large extent, control a hospital's occupancy by managing the number of elective surgical cases scheduled for admission, the authors write. The authors acknowledge that restricting these profitable procedures can cost hospitals money since they've become increasingly important to hospital finances in recent years.